1. Field of the Invention
The present invention relates to a III-nitride compound semiconductor (AlxInyGa1xe2x88x92xxe2x88x92yN, 0xe2x89xa6x,yxe2x89xa61) nanosized multiple quantum well light-emitting diode and a fabrication method thereof, and more particularly, to a III-nitride compound semiconductor nanosized multiple quantum well light-emitting diode having an amorphous silicon nitride (SiNx) layer (base) 200 including III-nitride compound semiconductor nanocrystals 230 spontaneously formed and a fabrication method thereof.
2. Background of the Related Art
An optical device or an electronic device based on III-nitride compound semiconductors (AlxInyGa1xe2x88x92xxe2x88x92yN, 0xe2x89xa6x,yxe2x89xa61) is fabricated in such a manner that a high-quality gallium nitride (GaN) thin film is basically grown on a sapphire substrate. The problem in this fabrication method is that sapphire that is expensive, hard and insulated is used as the substrate. Accordingly, the development of a substrate capable of replacing sapphire is required. The most typical substitute substrate is a silicon substrate. Studies on the silicon substrate are being widely carried out because the silicon substrate is cheap and conductive and it has an advantage in that a well-advanced electronic device based on silicon and an optical device based on gallium nitride (GaN) can be integrated with each other on the silicon substrate.
FIG. 1 is a schematic cross-sectional view of a conventional nitride semiconductor multiple quantum well light-emitting diode.
As shown in FIG. 1, the conventional nitride semiconductor multiple quantum well light-emitting diode is fabricated in such a manner that an n-type GaN 11 is deposited on a silicon substrate 10, a multiple quantum well composed of an InGaN 13 and a GaN 14 is formed on the n-type GaN 11 into an active layer 12, a p-type GaN 15 is formed thereon, and negative and positive metal electrodes 16 and 17 are formed on the n-type GaN and the p-type GaN, respectively. That is, the diode includes an n-type GaN layer, an active layer and a p-type GaN thin film as basic constituent elements.
However, the growth of the GaN thin film on the silicon substrate 10 has the following problems.
Firstly, silicon crystal and GaN crystal have a relatively large lattice mismatch of about 17% therebetween and a big difference in thermal expansion coefficient of 37% there between. These seriously deteriorate the quality of the GaN thin film formed on the silicon substrate.
Secondly, the growth of the GaN thin film having high quality on the silicon substrate is needed to integrate a silicon based electronic device and a GaN based optical device. However, the silicon substrate has a cubic crystalline structure and the GaN grown by a general technique has a hexagonal crystalline structure so that it is basically difficult to grow the high-quality GaN thin film on the silicon substrate due to a difference in crystalline structure.
Thirdly, an amorphous silicon nitride layer is spontaneously formed on the surface of the silicon substrate due to an undesired chemical reaction when the GaN thin film is grown on the silicon substrate, which makes it difficult to grow a high-quality GaN thin film.
Fourthly, in order to form the p-type GaN thin film having a high hole concentration, a technique for growing the high-quality GaN thin film is needed and the grown thin film should be thermally treated at a high temperature. This post-thermal treatment at a high-temperature for activating such a p-type dopant causes serious cracks on the thin film due to a large difference in thermal expansion coefficient between the GaN thin film and the silicon substrate.
An object of the present invention is to provide a high-quality nitride semiconductor nanosized multiple quantum well light-emitting diode having no crystalline defect and a fabrication method thereof.
Another object of the present invention is to provide a nitride semiconductor nanosized multiple quantum well light-emitting diode requiring no p-type GaN thin film and a fabrication method thereof.
To accomplish the objects of the present invention, there is provided a nitride semiconductor nanosized multiple quantum well light-emitting diode comprising: a silicon substrate 100; and an amorphous silicon nitride layer (base) 200 formed on the substrate 100 and including III-nitride compound semiconductor nano grains 230 spontaneously formed therein.
To accomplish the objects of the present invention, there is also provided a method of fabricating a nanosized multiple quantum well light-emitting diode using a III-nitride compound semiconductor, comprising the steps of: growing an amorphous silicon nitride (SiNx) layer on a silicon substrate; growing III-nitride compound semiconductor nanostructures on the amorphous silicon nitride layer; and growing-an amorphous silicon nitride cover layer on the amorphous silicon nitride layer and the nitride semiconductor nanostructures grown on the amorphous silicon nitride layer.